Fuel booster pump



Feb. 12, 1957 J. A. COMPTON ETAL 2,780,999

FUEL BOOSTER PUMP 2 Sheets-Sheet 1 Filed Dec. 12, 1951 fnuerzz o rts:James 0. Compi'oro 1 Feb. 12, 1957 J, A, COMPTON ErAL 2,780,999

FUEL BOOSTER PUMP 2 Sheets-Sheet 2 Filed Dec. 12, 1953 /a,oa0 20,000

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United States Patent FUEL BOOSTER PUMP James A. Compton, South Euclid,and Albert Paul, Cleveland, Ohio, assignors to Borg-Warner Corporation,Clucago, Ill., a corporation of Illinois Application December 12, 1951,Serial No. 261,296

4 Claims. (Cl. 103-113) This invention relates to a fuel booster pump,and more particularly to an arrangement for facilitating vaporelimination in a centrifugal type fuel booster pump.

Because the vapor pressure of the high octane fuel used in aircraft isrelatively high, that is, on the order of 6 to 7 p. s. i. at 100 F., asan aircraft rises from ground level to higher altitudes where thesurrounding air pressure becomes relatively low and possibly lower thanthe vapor pressure of the fuel, the fuel is subject to boiling andvaporization. This causes formation of bubbles in the fuel tank and atthe pump inlet and it renders exceedingly difiicult pumping of the fuelfrom the tank to the aircraft motor. To some extent, this undesirablecondition can be mitigated by pressurizing the fuel in the tank, butthis is considered dangerous and is particularly undesirable in militaryaircraft.

Rather than pressurize the fuel in the tank, another approach has beenused in some instances, and that is to effect, insofar as feasible, :1separation of the liquid and occluded gas and vapor, and to providemeans for returning to the tank the occluded gas and vapor. One methodof accomplishing this is disclosed in Burns Patent No. 2,513,992,wherein a propeller type pump is employed in tandem with a centrifugalpump, the propeller agitating the fuel and causing return to the fueltank of occluded air and vapor-thereby providing a supply of fuel to thecentrifugal pump which is substantially free of occluded air and vaporbubbles and thus the centrifugal pump does not fail by cavitation and isable to develop the required pressure to the main fuel pump associatedwith the aircraft carburetor or fuel injection system. However, in thislatter type of arrangement a considerable portion of the fuel is alsoreturned to the fuel tank, and furthermore, because of the unavoidablelow output of the propeller type pump, the fuel supplied to thecentrifugal pump is still at or very near the boiling point so that theperformance of the centrifugal pump is limited by the adverse inletconditrons.

Another arrangement which has been used in meeting this problem has beento employ a centrifugal type pump in combination with a liquid ring typepump, such as illustrated in Jennings Patent 1,718,294 and Adams Patent2,362,954, the liquid ring pump being employed for the purpose ofremoving occluded gas and vapor gathering at the inlet or eye of thecentrifugal pump. Unless this vapor which tends to gather in a bubble atthe inlet of the centrifugal pump is removed, the centrifugal pump isvery likely to fail.

With systems such as the two just described, efliciency is relativelylow since a considerable portion of the fuel is returned to the fueltank and furthermore, because of the necessity of providing a secondpumping arrangement, the system is naturally heavier and more expensivethan a system wherein a centrifugal pump alone would be able to supplythe final fuel pressure.

In accordance with the present invention, as applied in a fuel boosterpump of the type employing a centrif- "ice ugal pump as the fuelpressure boosting mechanism, a sleeve is located in the inlet portformed in the housing of the centrifugal pump and projects axiallyinwardly toward the impeller to define with the adjacent wall of thepump inlet port an annular chambered area adjacent the lower extremitiesof the centrifugal pump impeller. During the operation of thecentrifugal pump occluded air, gas and vapor entrained with the liquidfuel entering the pump inlet are forced into the annular chamber soprovided. A venting passage communicated to the fuel tank or to asuitable gas handling pump, is connected to this annular chamber andpermits escape of the gas, air and vapor which accumulate therein undermoderate pressure.

Other objects and advantages of the present invention will be apparentfrom the following detailed description thereof taken in conjunctionwith the drawings wherein Fig. l is a vertical sectional view, partly inelevation, showing a combined centrifugal-liquid ring type booster pumphaving associated with the inlet thereof a sleeve in accordance with thepresent invention,

Fig. 2 is a transverse sectional view taken substantially along the line2-2 of Fig. 1,

Fig. 3 is a graph indicating relative performance characteristics of apump of the type illustrated in Fig. l with and without the inlet sleeveof this invention, and

Fig. 4 is a fragmentary view, similar to Fig. 1, illustrating theincorporation of the inlet sleeve of this invention in a simple,centrifugal booster pump.

Referring now to Fig. 1, a combined centrifugalliquid ring type boosterpump is there illustrated comprising generally a motor 5 for driving ashaft 6 to which is ailixed a liquid ring impeller 7 and a centrifugalimpeller 8, the whole being enclosed within a housing 9 and located, inthe embodiment illustrated, within a tank it A suitable mounting plate11 is -provided for securing the housing 9 in position in the tank. Themotor 5 ordinarily is an electric motor and is controlled remotely, asis well known in the art. Fluid entering this bootser pump from the tankpasses through a screen 12 mounted about the open lower portion of thehousing of the pump and moves at first radially inwardly and thenupwardly through the inlet port opening 13 of the centrifugal portion ofthe pump, entering the lower portion of the volute chamber 14, formingthe pumping chamber of the centrifugal portion of the pump. Fluid underpressure is discharged through volute passage 15 which is connected by asuitable conduit (not illustrated) to the engine or other apparatus withwhich this booster pump may be associated in use.

Since the occluded air and vapor entering the centrifugal pump with thefuel tends to collect at the eye, that is, the center of the inlet ofthe centrifugal pump, it is sometimes the practice, as pointed outhereinbefore, to provide a liquid ring impeller type pump, such as thepump 7, for the purpose of evacuating the entrained vapor and gas.Communication is afforded between the liquid ring pump and the eye ofthe centrifugal impeller 8 by a suitable passage 16 provided in the pumphousing, connected to chamber 17 enclosing the liquid ring impeller 7.In prior art arrangements this passage 16 has been connected directly tothe inlet area of the impeller 8.

However, it has been found in accordance with the present invention thatelimination of gas and vapor is more complete and at the same timesegregation or separation of the gas and vapor from the liquid portionof fuel is more nearly perfect if there be provided at the inlet of thepump a sleeve, indicated at 20, whereby gas and vapor tending to move ina direction opposite to the direction of movement of the fuel (the gasand vapor being lighter) may be collected and segregated.

Referringmore in detail than-to Fig. 1', it will be seen of gaseousmaterials.

' that at the inlet of the ce gal puns there mounted portion 21 and alower outwardly flanged portion 22 ereby the s eeve i ecurely ocate athe entrance to the centri u l pump chamber. Th lower inn r orn r. 22;;afth sleeve is rounded o pro ide desirable fl w n it ns h radi lly entersi e f the upper portion 21 of the sle 20 defines ith the djac n Wall ofhe n r tus Pump hamber an an ular cham er 23 of ri ngula r ssct on, intwhich chambe 23 as and vapor are f rced under Pres ure during the peraton o h ent ifugal phrnphus, rather; tha ha e th ga an ap r e n to theeye of th Pump an he aga Pa ial y ith he fue n isuid stat nt ring hepump, t e a and apor are tram d the ann lar hamb r and PYIi1 i from retrning to he inlet of the centrifugal pump. It will be apparent that inthe sen of sl e .0 ir andaas ent ain d with he fu l o ld nd no on y togathe a in at the inle of h ntr fuga P mp and part thereof be retrievedby h liquid r n mp 7 u @1 9 se ne ould be mix d a a with t e f er e cntrifugal Pui-npehd h c rri d along with the liquid portion of the fueldischarged through the velute passa e 5 To the ex e t tha this tendencyto em n an be m n mized, h etfieiehsy of the pump is directly increased.Thus by preventing re-entrance of the segregated gas and'vapor by meansof the sleeve 2%, a m r mpr e h it'ih ef iciency provided.

The location of trapping groove or recess 23 is importent n e it m be loated so hat the a vapor and air separated from the liquid 'pgrtion ofthe fucl by the centrifugal pumping action will tend to gather therein.It has been determined that the trapping recess 23 should be located asnearly as possible at the narrowest diam ter f the centrifugal pumpingChamber, that is, in practice, immediately adjacent the eye of theimpeller, The depth of chamber 23, in general, is best determined byactual test and experimentation. However, it will be evident that thetubular portion 21 must extend a substantial distance beyond the inneredge of the inlet port sp as to define an effective trapping area. Itmust, on the other hand, not extend so far as to interfere withthedischarge of liquid from the centrifugal pump. In the embodimentillustrated in Fig. l, the lower portion of the impeller S is actuallycentrally recessed as indicated at 81; to rcceive the pp rm t Po ti n ot e sl e in ot er WQIQS, h r m y h a s i h er p of th s ee e and of theimpeller.

In h em dime il ust ted in Figi apo and gas in rapp c s .23 re coll ed na drain P ssa e 24, formed he l er pert n o he h usin and 5 9mmunicatingwith the lower side of the recess 23, and are i hd a rom th pa s ge by eq id n pump,

which, as is well known, is well adapted to the pumping Passage 24communicates at its left, upper end with passage 16 leading to the inletof the liquid ring impeller. The liquid ring pump discharges directlyinto the tank 10.

It will be noted that a narrow cross-section, drain passage is formed inthe housing on the opposite side of the inlet from the passage leadingto the liquid ring pump and communicates with the lower side of chamber23. This small passage is provided to drain liquid, particularly water,which may gather in the chamber 23 and under freezing conditions preventoperation of the centrifugal pump after a period of nonoperation, and isrequired because of the incorporation of the sleeve 20 in the nle of thePump, since t u the s ee e, iquid ac umulating at the inlet would runback in the tank. Passage 25 i p f a y mad qu t smal n c ess seet-i n toavoid interfer nce With the opera ion o t e pump- Referring now to thegraph presented in Fig. 3, the dotted line curve A indicates theprcssureoutpnt or performance of a pump such as that illustrated-in Fig.1

a esee ithout the idet slee e of this in ention.- reih curv A it will beapparent that the pump begins to fail at approximately 15,000 ft. andfailure is substantially complete at approximately 17,500 ft. In mostinstances such failure is due to the accumulation of air, gas and vaporat the inlet of the centrifugal pump more rapidly than it caneffectively be removed by the scavenging liquid ring pump. It will benoted that curve A has been shown as commencing again and the pressureoutput rising to the approximate value attained prior to failure. Thisrecovery phenomenon is due to the fact that if the primary pump withwhich the booster pump is associated continues to e driven t en thispump may pump the ai and ap accumulating at the inlet 9f the centrifugalpump through the fuel line and in this manner clear the'centrifugalpump. Ultimately, the liquid ring pump might be able to accomplish thisalso. This does not necessarily occur but does occur sometimes. However,even under ideal conditions ending to ma e f r ah recov pe o m n the ewill be a substantial period of time during which no fuel is actuallypumped. If this period is of suiiicient duration, then where such aboosterpump is employed with a jet engine, it will be apparent that aflame out, that is, extinction of thejet flame, may occur with resultanttotal failure of the engine. 'In any event, such intermittent operationis extremely dangerous and particularly so since once the necessaryconditions are present it will occur not once bu pea ed The continuouscurved line B represents the performance of a fuel pump of the typeshown in Fig. 1 provided with the inlet sleeve 20. From curve B it willbe evident that there is no failure and that the pressure is continuous.Fluctuations represented in curve B are actual and not theoretical,being due to flight conditions including change in the pressure againstthe fuel in the tank by the air as the aircraft goes to higher altitudesand changes in the temperature of the fuel being pumped due to the 7. Ithas been determined that due to the pressure developed by thecentrifugal pump in the centrifugal pumping chamber, which pressure isexerted to some extent against the air and gas trapped in the annularchamber 23, under many operating conditions'this pressure is of itself.eliective to cause return to the tank of air and gas trapped in chamber23 without the necessity of providing'the gas evacuating pump shown inFig. 1. This embodiment, of course, has a real advantage over theembodiment shown in Fig. 1 in that the pump is both lighter and cheaper.

In the embodiment illustrated in Fig. 4, therefore, instead of providingthe passage 16 through the housing connecting the drainage passage 24with the liquid ring impeller, a port 26 is formed in the housing andthe drainage passage 24 is connected thereto, the port 26 opening intothe tank 19 and permitting direct return Since during the operation orof trapped air and gas. the booster pump, the fuel in the tank is undersuction whereas the air, vapor and gas collected in the recess 23 isunder some pressure above the inlet pressure value, it will be apparentthat there is no danger of fuel being sucked into the pump through theport 26, but rather that there will be a return flow from the pumptrapping area 23 to the tank.

An additional advantage obtained through the use of the sleeve 20 isthat the inlet condition to the centrifugal impeller is materiallyimproved. In the absenceof the sleeve the centrifugal impeller tipsagitate the fuelas it enters this pump and this produces turbulencewhich in turn reduces the overall pumping efliciency of the centrifugalpump.

Where herein the various parts of this invention have been referred toas being located in a right or a left position or in an upper or lowerposition, it will be understood that this is done solely for the purposeof facilitating description and that such references relate only to therelative positions of the parts as shown in the accompanying drawings.

While but two embodiments of this invention have been shown anddescribed it will be understood that many changes and modifications maybe made therein without departing from the scope of the presentinvention.

What is claimed is:

1. A combined fuel booster and vapor eliminating pump for pumpingvolatile fuels, including a pump casing having a centrifugal pumpingchamber formed therein and an inlet and an outlet port connected to saidchamber, a centrifugal impeller rotatably mounted in said chamber andhaving blades conforming to the contour of said chamber, an elongatedsleeve mounted in said inlet port and providing at its inner surface aninlet throat, a portion of said sleeve extending into said chamber inoverlapping relation with said impeller to prevent the return of vaporto the center of said impeller, the outer wall of said portion of saidsleeve defining with the adjacent inner Wall of said casing a vaportrapping recess, a portion of said blades extending into said trappingrecess to provide communication between said recess and the remainder ofsaid blades, and passage defining means for permitting vapor trapped insaid recess to escape therefrom, said trapping recess being locatedradially inwardly of the maximum diameter of said chamber.

2. A combined fuel booster and vapor eliminating pump for pumpingvolatile fuels, including a pump casing having a centrifugal pumpingchamber formed therein and an inlet and an outlet port connected to saidchamber, a centrifugal impeller rotatably mounted in said chamber andhaving blades conforming to the contour of said chamber, an elongatedsleeve mounted in said inlet port and providing at its inner surface aninlet throat, a portion of said sleeve extending into said chamber inoverlapping relation with said impeller to prevent the return of vaporto the center of said impeller, the outer wall of said portion of saidsleeve defining with the adjacent inner wall of said casing a vaportrapping recess, a pottion of said blades extending into said trappingrecess to provide communication between said recess and the remainder ofsaid blades, and passage defining means for permitting vapor trapped insaid recess to escape thereform, said trapping recess being locatedradially inwardly of the widest portion of said chamber.

3. A combined fuel booster and vapor elminating pump for pumpingvolatile fuels, including a pump casing having a centrifugal pumpingchamber formed therein and an inlet and an outlet port connected to saidchamber, a centrifugal impeller rotatably mounted in said chamber andhaving blades conforming to the contour of said chamber, an elongatedsleeve mounted in said inlet port and providing at its inner surface aninlet throat, a portion of said sleeve extending into said chamber, theouter Wall of said portion of said sleeve defining with the adjacentinner wall of said casing a vapor trapping recess, a portion of saidblades extending into said trapping recess to provide communicationbetween said recess and the remainder of said blades, and passagedefining means for permitting vapor trapped in said recess to escapetherefron and a drain passage connected to said recess for preventingaccumulation of liquid therein.

4. in a fuel booster pump including a housing having a pumping chamberformed therein and an inlet and an outlet port communicating with saidchamber, a centrifugal impeller rotatably disposed in said chamber forpumping liquid from said inlet port to said outlet port and havingblades conforming to the contour of said chamber, an inner sleevelocated at said inlet port and defining within said housing a trappingchamber, a portion of said blades extending into said trapping chamberfor providing opening communication between the chamer and the remainderof said blades, and a vent passage defining means connected to saidtrapping chamber.

References Cited in the file of this patent UNITED STATES PATENTS1,139,042 Lehne et al May 11, 1915 2,306,300 Curtis Dec. 22, 19422,581,828 Adams Jan. 8, 1952 FOREIGN PATENTS 597,751 Great Britain Feb.3, 1946 630,932 Germany May 14, 1936 695,713 Germany Aug. 31, 1940

